Several tests to detect analytes in samples are known in the art. Some examples are described in U.S. Pat. No. 5,985,675, issued Nov. 16, 1999; U.S. Pat. No. 6,319,466, issued Nov. 20, 2001; U.S. patent application Ser. No. 10/289,089, filed Nov. 6, 2002 (based on U.S. Provisional Application 60/332,877, filed Nov. 6, 2001); U.S. patent application Ser. No. 09/961,998, filed Sep. 24, 2001; U.S. Pat. No. 7,410,808, issued Aug. 12, 2008; U.S. Pat. No. 7,785,899, issued Aug. 31, 2010; and U.S. Pat. No. 7,863,057, issued Jan. 4, 2011, all of which are incorporated herein by reference in their entireties and elements of which may be useful in embodiments described herein. Sample and testing devices and methods are also known in the art including those described in U.S. Pat. No. 5,965,453, issued Oct. 12, 1999, incorporated herein by this reference in its entirety and elements of which may be useful in embodiments described herein.
Tests to detect one or more analytes in a sample using receptors, such as antibodies, that include detectable components can be designed in variety of formats. One such format is known as a sandwich assay. In a typical sandwich assay format the analyte to be detected becomes bound by two receptors, one of which carries a detectable component—the label receptor—and the other of which captures the analyte to allow detection. Sandwich assays, however, are known to exhibit what is known in the art as a hook effect. The hook effect is a characteristic of a sandwich assay which is observed at higher concentrations of an analyte that is being detected. The hook effect can be caused by an overwhelming of a capture agent by unlabeled analyte thereby blocking detection of labeled analyte. The hook effect can, therefore, lead to a false negative result. Applicant has discovered that it is advantageous to provide a test that does not suffer from the hook effect and that can detect large molecules, such as proteins, including allergenic proteins, in a sample, such as a food sample.
Separate from the hook effect, is the problem of steric hindrance which is sometimes observed in lateral flow tests, and other tests detecting high molecular weight molecules, such as molecules of molecular weight greater than about 5,000, such as proteins, for example casein and beta-lactoglobulin. In particular, effective functioning of the test can be impaired by the interference of the large molecule with binding sites when protein binding is being detected, or when a large molecule is involved in a test in general. Applicant has discovered that it is advantageous to provide a test that can detect large molecules, such as allergenic proteins, in a sample, such as a food sample, that does not suffer from such steric hindrance or, at least, reduces the influence of steric hindrance.
Therefore, Applicants desire systems and methods for detecting high-molecular weight substance without the drawbacks presented by the traditional systems and methods.